Tooth sensitivity, including dentinal hypersensitivity, has become identified as a common problem among consumers. Dentinal hypersensitivity is a condition where dentin is exposed due the lack of soft tissues covering the surfaces. The exposed dentin includes small tubules which are susceptible to triggering of a pain response from a variety of stimuli such as heat, cold, sour taste, or pressure. The level of pain can range from an ache or soreness to a shooting pain. The most common approach for over-the-counter, at-home treatment of dentinal hypersensitivity is the use of dentifrices containing desensitizing agents such as SENSODYNE PRONAMEL (contains 5% potassium nitrate) and NOVAMIN (contains bioactive glass). While such products can provide some relief, reduction of sensitivity through dentifrice use alone is limited for several reasons including: inherent limitations on the contact time of the dentifrice to the exposed dentin (as brushing time may be relatively short); dilution of the desensitizing agent by saliva; typical usage includes rinsing one's mouth out after brushing reducing the amount of desensitizing agent delivered to the tooth; and inherent limitations on the amount of desensitizing agent that may be stably formulated into a dentifrice formulation. A need therefore exists for an improved treatment for dental hypersensitivity that can be easily performed at home.
Oxalate salts can act as dentinal tubule blockers that can thereby be useful for the treatment of dental hypersensitivity. Potassium oxalate is a preferred desensitizing agent as it forms calcium oxalate upon delivery to the open tubules. Formation of the calcium oxalate blocks the dentinal tubules and may prevent environmental stimuli from causing sensitivity pain.
A product called SUPERSEAL is a commercially available dental sensitivity treatment product available from Phoenix Dental. The SUPERSEAL product is in liquid form and is sold in a small bottle. The bottle contains a 2.9% solution of a potassium oxalate salt, K3H(C2O4)*2H2O at a pH of 1.5 (approximately 1.0% of oxalate ion). The instructions for use include painting or swabbing the liquid in the oral cavity. Although the product does help with dental hypersensitivity, it can be difficult for consumers to know how much to apply and/or to target a single area for treatment, and contact time of the potassium oxalate at the sensitivity site may be transient due to dilution with saliva.
Similarly, a LISTERINE brand rinse is commercially available in the United Kingdom that contains dipotassium oxalate and has a pH of 4.3. Again, the presence of the potassium oxalate in the mouth is transient and here, it is considerably difficult to target a particular area of sensitivity with a rinse product.
The combination of adhesive-building polymer with potassium oxalate has been attempted in another commercial tooth desensitizing product, SENZZZZZAWAY, available from Majestic Drug (New York, USA). SENZZZZZAWAY is a single-use blister packed product containing a composition that includes a CARBOPOL (CARBOPOL is the trade name for a general class of high molecular weight homo and co-polymers of acrylic acid crosslinked with a polyalkenyl polyether, commercially available from Lubrizol Advanced Materials, Inc. (Ohio, USA), thickener and 2.5% (as added) of an oxalate salt (KHC2O4+HNO3) at a pH of 0.7. The product is packaged with a small brush and the instructions include brushing the product onto the area to be treated. If potassium oxalate is applied to the wrong part of the oral cavity and/or for too short of a period of time, it is possible that no benefit is garnered or that the crystal deposition occurs at the wrong site. A need therefore still exists for a sensitivity product that can reach the desired location, deliver the desired chemistry, and for the desired amount of time. The prior literature discloses that potassium oxalate works but also has disclosed it as being ineffective for dentinal tubule blocking. Without being limited by theory, it is now believed that some of the ineffectiveness was wrongly associated with the potassium oxalate mechanism itself when it was likely just the wrong selection of contact time, delivery device, pH, and the like.
Strip-form oral care delivery systems are commercially available, such as tooth-whitening strips including those sold under the name CREST WHITESTRIPS by the Procter & Gamble Company (Cincinnati, Ohio, USA). The popularity of the strip format has expanded to include strips for fluoride treatment and sensitivity treatment (for example, SHEER FLUORX and SHEER DESENZ strip tooth treatment products, both commercially available from the CAO Group, Utah, USA).
Further, the literature discussing delivery systems for tooth-whitening also often generally disclose that the same delivery systems may be used with sensitivity agents. However, due to the fundamental differences between whitening agents and potassium oxalate, it has been surprisingly found that the compositions previously found to be useful in conjunction with whitening strip products are unsuitable for the delivery of potassium oxalate.
A tooth sensitivity delivery kit including a preformed tray and a bulky foam strip (approximately 6 cm long, 1 cm tall, 1 cm thick) impregnated with a potassium oxalate solution that sits inside the tray is commercially available under the trade name REMESENSE from Sylphar (Belgium). Although providing some efficacy, the REMESENSE tray system is bulky and uncomfortable for consumers during use. Further, due to the porosity of the impregnated foam, the potassium oxalate solution settles (due to gravity) into the lowest portion of the foam, making application to the gum line difficult (if not impossible) and the delivery system only suited for use with the upper arch, not the lower arch. Further, it is difficult to provide targeted relief to an area in need of treatment through the use of the REMESENSE tray and foam.
The need therefore exists for a dentinal hypersensitivity treatment product that can provide directed, sustained delivery of a desensitizing agent to a desirable area in the oral cavity, for a period of time sufficient to provide significant tubule blockage and subsequent sensitivity relief.